The study is a first step to see if the vaccine appears safe enough for larger tests needed to prove whether it will protect. Even if the research goes well, it is expected to take over a year before any vaccine could be widely available.

Last month, the first safety test in people of a different vaccine candidate began in Seattle. It was developed by the National Institutes of Health and Moderna Inc.

Numerous other research groups are attempting to make vaccines against COVID-19 using a variety of different methods in hopes at least one will offer protection.

Inovio's approach is what's called a DNA vaccine, made using a section of the virus' genetic code packaged inside a piece of synthetic DNA.

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This undated electron microscope image made available by the U.S. National Institutes of Health in February 2020 shows the Novel Coronavirus SARS-CoV-2, orange, emerging from the surface of cells, green, cultured in the lab. Also known as 2019-nCoV, the virus causes COVID-19. The sample was isolated from a patient in the U.S. (NIAID-RML via AP)